(1) Field of the Invention
The present invention relates to an evaporated fuel treating device.
(2) Description of Related Art
Hitherto, as an evaporated fuel treating device (hereinafter referred to as the canister) that temporarily adsorbs fuel components in an evaporated fuel so as to restrain the evaporated fuel from being released to the atmosphere from an automotive fuel tank or the like, there has been known a canister 101, which has a case 105 with a tank port 102, a purge port 103 and an atmospheric port 104 formed therein, as illustrated in FIG. 16. The interior of the case 105 is partitioned into a plurality of chambers 106 and 107, and a first adsorbent layer 109 and a second adsorbent layer 110 are formed by filling the chambers 106 and 107 with activated carbon 108. A nonwoven cloth 111 is provided between the second adsorbent layer 110 and the atmospheric port 104 to prevent the fine powder of the activated carbon 108 constituting the second adsorbent layer 110 from leaking out into the atmospheric port 104 (refer to, for example, JP-A-2008-202604 and JP-A-2004-60584).
Recently, in the canister, the second adsorbent layer 110 positioned most closely to the atmospheric port 104 has been formed such that an increased ratio L/D between a vertical length L in FIG. 16 and a diameter D of a cross-section in FIG. 16 is obtained thereby to reduce the amount of an evaporated fuel emitted to the atmosphere.
The aforesaid conventional canister 101 is formed such that the transverse sectional area of the second adsorbent layer 110 is substantially equal to the surface area of the nonwoven cloth 111. Therefore, with the reduction of the transverse section area of the second adsorbent layer 110 in order to increase the L/D ratio, the surface area of the nonwoven cloth 111 would be decreased. As illustrated in FIG. 17, however, the pressure loss in the nonwoven cloth 111 at the same flow rate increases as the surface area decreases. This poses a problem that reducing the transverse section area of the second adsorbent layer 110 to increase the L/D ratio inconveniently leads to deteriorate refueling performance.